Marine propulsion device

ABSTRACT

A marine propulsion attachment ( 7 ) for a brush cutter device having an engine and a first shaft ( 2 ) mounted within a tube ( 3 ) and rotatable by said engine, said attachment ( 7 ) comprising a propeller ( 10 ) connected to a second shaft; a protective shroud ( 12 ) for said propeller ( 10 ) and rotatably supporting said second shaft; and connection means to interconnect said shafts to permit their simultaneous rotation by said engine.

FIELD OF THE INVENTION

[0001] The present invention relates to a marine or maritime propulsiondevice and, in particular, to a brush cutter device with a propellerattachment that is mounted to a marine or riverine craft to propel itover or through the water.

BACKGROUND OF THE INVENTION

[0002] The standard outboard motor is widely used for marine or riverinepropulsion. However, when all that is required is some propulsion meansto propel a boat, or some other marine craft, relatively shortdistances, the purchase of an outboard motor is often an expensiveoption.

[0003] For example, owners of yachts or similar vessels who must moortheir vessel in deep water use some form of tender to access theirmoored vessel. At present, the tender used can be an oar propelledrowing boat or a boat powered by an outboard motor. Upon reaching themoored vessel, the tender is attached to the mooring to prevent itdrifting away. When an outboard motor is used to propel the tender, theoutboard motor is usually lifted off the tender and loaded onto theyacht to ensure that an opportunistic thief does not disappear with theunattended tender and outboard motor. However, due to the weight of themotor, this is often a difficult and laborious task. On the other hand,this may be less tiring than physically rowing out to the mooring sitein a rowing boat. Further, the upkeep and running costs for an outboardmotor are relatively high considering that it is primarily being usedmerely to propel the tender to the moored vessel, not to mention thecost of purchasing an outboard motor for this purpose initially.

OBJECT OF THE INVENTION

[0004] The object of the present invention is to disclose a portable,light-weight marine or riverine propulsion device that is thought to becheaper to buy than a typical outboard motor.

SUMMARY OF THE INVENTION

[0005] The object is preferably achieved with a pre-existing brushcutter device of the user who is then able to purchase a propellerattachment at low cost and then assemble a modified brush cutter deviceincluding the propeller. Preferably, the tube housing the shaft of thepropulsion device is mounted on a swivel attached to the stern of thecraft. This permits the person controlling the propulsion device to varythe angle at which the propeller shaft engages the water. The swivelallows rotation of the tube in azimuth relative to the swivel in orderto steer the craft. Therefore, there is no need for a rudder. The depthat which the propeller sits in the water may also be varied by adjustingthe altitude angle of the tube. This is particularly useful whentravelling across shallow water. Additionally, the swivel preferablypermits the tube to slide longitudinally through the swivel to bring thepropeller either closer to, or further from, the “stern” of the craft.

[0006] The attachment for a brush cutter device is preferably able to bedisconnected from the shaft attached to the engine of the brush cutter.In this way, the main component of the brush cutter containing theengine and to which the marine propulsion attachment is connected has adual purpose in that either the abovementioned propeller attachment or aconventional lawn or vegetation trimming blade cutting attachment can beconnected.

[0007] Furthermore, the use of this marine propulsion device is notlimited to the propulsion of boats and has equal application in thepropulsion of surfboards, surf skis and like craft. Traditionally, craftwithin this category have relied on a user paddling, the wind or thewaves to propel them through the water. This can often be a laborious ortime consuming method of propulsion.

[0008] In accordance with the first aspect of the present inventionthere is disclosed a marine propulsion attachment for a brush cutterdevice comprising an engine and a first shaft rotatably mounted within atube and rotatable by said engine, said attachment comprising apropeller connected to a second shaft, a protective shroud for saidpropeller and rotatably supporting said second shaft, and connectionmeans to interconnect said shafts to permit their simultaneous rotationby said engine.

[0009] According to the second aspect of the present invention there isdisclosed a marine or riverine craft propulsion device, said devicecomprising a brush cutter having an engine, a shaft rotatably mountedwithin a tube and rotatable by said engine, a propeller rotatablymounted within a protective shroud for said propeller and rotatable bysaid shaft, a mounting swivel adapted to be mounted on said craftreceiving said tube and permitting longitudinal movement of said tuberelative to said swivel, rotation of said tube in an azimuth planerelative to said swivel, and rotation of said tube in altitude relativeto said swivel.

[0010] According to the third aspect of the present invention there isdisclosed a surfboard, surf ski or like craft having an upper personsupporting surface and an under surface, a brush cutter device having anengine, a shaft rotatably mounted within a tube and rotatable by saidengine, a propeller rotatably mounted within a protective shroud forsaid propeller and rotatable by said shaft, said tube and shaft beingsubstantially aligned with the longitudinal axis of said craft andpassing therethrough between said surfaces, said engine being locatedabove said upper surface and said propeller being located below saidlower surface, whereby said propeller is rotatable by said engine toadvance said craft through water, and said craft is steerable byaltering the weight distribution of the person using said surfboard,surf-ski or like craft.

DESCRIPTION OF THE FIGURES

[0011] Three embodiments of the present invention will now be describedwith reference to the drawings in which:

[0012]FIG. 1 is a perspective view of a prior art brush cutter with itsthe brush cutting attachment disconnected from the engine-driven shaft,

[0013]FIG. 2 is a perspective view of a first embodiment of the marinepropulsion attachment,

[0014]FIG. 3 is a side perspective view of the attachment of FIG. 2,

[0015]FIG. 4 is an end view of the attachment,

[0016]FIG. 5 is a cross-sectional view of the attachment taken along theline V-V of FIG. 4,

[0017]FIG. 6 is an enlarged view of the interior of a drive reductiongear box able to be located within the attachment of FIGS. 2-5,

[0018]FIG. 7 is a partial view of an alternative pair of bevelled gearsfor use in the gear box of FIG. 6,

[0019]FIG. 8 is a side view of a dingy embodiment in use,

[0020]FIG. 9 is a plan view of the dingy of FIG. 8,

[0021]FIG. 10 is a side view of a canoe embodiment in use,

[0022]FIG. 11 is a side view of a surf-ski embodiment,

[0023]FIG. 12 is a plan view of the surf-ski of FIG. 11,

[0024]FIG. 13 is a partial inverted plan view of the surf-ski of FIG.11,

[0025]FIG. 14 is a partial plan view of the front of the surf-ski ofFIG. 11,

[0026]FIG. 15 is a view of a swivel for use in the canoe or dingyembodiments.

DETAILED DESCRIPTION

[0027] Turning now to FIG. 1, it is evident that the prior art brushcutter 1 takes the form of a shaft 2 housed within a tube 3 andconnected such that the shaft 2 is rotatable by an engine 4. The enginedrives the rotation of the shaft 2 via a centrifugal clutch(conventional—but not illustrated). A brush cutting attachment 5 can beconnected to, and disconnected from, the free end 6 of the shaft 2 byvarious conventional means including threaded engagement or fasteners ofvarious types (not illustrated).

[0028] A first form of a marine propulsion attachment 7 is illustratedin FIGS. 2-5. The attachment 7 takes the form of a twin blade low pitchpropeller 10 fixed to a propeller shaft 8. The shaft 8 is rotatablymounted in an end bearing 9 supported by a three-armed spider 11. A pairof longitudinally spaced cylindrical shrouds 12 support the spider 11and protects persons from injury by coming into contact with the tips ofthe blades 13 of the propeller 10. Additionally, the protective shrouds12 and their supporting struts 19 guard the blades 13 against damagefrom coming into contact with submerged objects while the propeller 10is rotating.

[0029] A sleeve 15 having a bearing 16 for the shaft 2, is retained inthe free end of the tube 3 by a mechanical clamp 14 in an interferencefit. The shaft 2 is secured to the propeller shaft 8 by means of a grubscrew 17, or similar. As the engine 4 drives the rotation of the shaft 2which is in turn connected to the propeller shaft 8, the propeller 10fitted rotates simultaneously with the shaft 2.

[0030] The speed of the shaft 2 generated by the engine 4 isapproximately 6,000 revolutions per minute (rpm) since this is apractical speed for use of the device as a brush cutter. However, whenused for marine propulsion, it is sometimes desirable for the enginespeed to be lowered in order to rotate the propeller 10 at a slowerspeed. This produces less cavitation and enables blades of greater pitchto be used. Thus a shaft speed of approximately 3,000 rpm is preferableto accommodate such propellers. This reduction in engine speed isachieved through the incorporation of a drive reduction gear box 20, theinterior of which is illustrated in FIG. 6. The gear box 20 ispreferably incorporated into the attachment 7 at the junction of theshafts 2 and 8.

[0031] As seen in FIG. 6, the gear box 20 includes a keyed output shaft21 and a keyed input shaft 22. Mounted on shafts 21, 22 arecorresponding gear wheels 23, 24. The shafts 21, 22 are also supportedby bearings 25, 26 and 27, 28 respectively. The output shaft 21 is alsopreferably provided with a substantially waterproof seal 29.Alternatively, as indicated in FIG. 7, the gear wheels 23, 24 can bereplaced by beveled gears 33, 34.

[0032] A first embodiment of a marine craft is illustrated in FIG. 8, inwhich the tube 3 is mounted in a swivel 36 at the stern 37 of a dingy38.

[0033] The swivel 36 is shown in FIG. 15 and includes a substantiallyU-shaped bracket 50 configured to mount to the stern 37. Although notillustrated, in use the U-portion is placed over the stern 37 with asleeve 51 disposed on an outer arm of the bracket facing away from thestern 37. A threaded ram 52 is then wound to secure the bracket to thedingy 38 where an abutment surface 53 attached to the ram 52 clamps thestern 37 to the bracket 50.

[0034] The sleeve 51 receives a rotatable shaft 54. The shaft 54includes a groove at one end for receiving a retaining clip 55 to(upwardly) restrain the shaft 54 within the sleeve 51.

[0035] The other end of shaft 54 includes a receiving bracket 56 havinga pair of opposing spaced apart apertures 57. A tab 58 extending from ahead member 59 includes an aperture 60, the tab 58 being configured tobe rotatably and retainingly engaged in the space between the aperture57 by an axle 61. Axle 61 is itself retained by a head 62 at one end anda retaining clip 63 at the other.

[0036] The head 59 further includes a pair of jaws 64 which clamp on aportion of the shaft 3 to thereby retain it. The jaws 64 are hingedlymounted so that one jaw is attached to the tab 58 and a screw 65 andwing nut 66 engage a tab 67 on each jaw to clamp the jaws to the shaft 3or allow the jaws to open about their hinge to release the shaft 3.

[0037] When retained by the jaws, the shaft 3 is rotatable in the planeof the water by rotation about the shaft 54 and rotatable perpendicularto the plane of the water by rotation of the swivel 36 about axle 62.

[0038] No matter whether the user sits, kneels or stands, the swivel 36allows the altitude angle of the tube 3 to be varied so as to allowmanual positioning of the propeller 10 in the water by either raising orlowering the engine 4. This is indicated by arrows A in FIG. 8. Thedepth of engagement between the water and tube 3 is also adjustable bysliding the tube 3 longitudinally through the swivel 36 to alter thedistance of the propeller 10 from the stern 37 of the dingy 38. This isindicated by arrows B in FIG. 8. As seen in FIG. 9, the swivel 36 alsoallows rotation of the tube 3 in azimuth relative to the swivel 36 tosteer the dingy 38 left or right in the same way a rudder steers amarine craft. This is indicated by arrows C in FIG. 9.

[0039] A second embodiment of a canoe 40 is illustrated in FIG. 10 wherethe tube 3 is mounted on a swivel 36 as before but offset from the sideof the canoe 40. In this embodiment, the bracket 50 of the swivel 36 isconfigured to mount to the side wall of the canoe 40.

[0040] A third embodiment of a surf-ski 43 is illustrated in FIGS. 11-14where tube 3 and shaft 2 pass through the centre of the surf-ski 43. Theengine 4 is above the supporting surface 44 and includes only oneprotective shroud 12 which is below the immersed surface 45. Thesurf-ski 43 is steerable by the user changing his weight distribution onthe supporting surface 44.

[0041] The engine 4 is also encapsulated by a waterproof protectivecover 47 that guards the engine 4 from being immersed when the surf-ski43 moves through waves. The waterproof protective cover 47 is alsofitted with a conventional snorkel breathing attachment (notillustrated) that allows air to pass through it and into the spacedefined by the interior of the waterproof protective cover 47 withinwhich the engine 4 is contained. The snorkel contains a valve thatallows the flow of air into the space to the engine 4 but prevents waterfrom passing through the snorkel when the surf-ski 43 travels throughwaves. Such snorkels are conventionally found on many jet-skis.

[0042] It will be apparent that the above described embodiments providemany advantages. A low cost and light-weight propulsion unit is providedwhich is suitable for many applications in rivers, lakes, estuaries andthe like.

[0043] The foregoing describes only three embodiments of the presentinvention and modifications, obvious to those skilled in the art, can bemade thereto without departing from the scope of the invention. Forexample, in addition to the swivel 36, the engine end of the tube 3 canbe supported by the free end of a tiller like arrangement. Similarly, anelectric motor can replace the petrol engine 4 and the term ‘engine’ isunderstood to include such a motor.

[0044] The term “comprising” as used herein in is used in the inclusivesense of meaning “having” or “including” and not in the exclusive senseof “consisting only of”.

1. A marine propulsion attachment for a brush cutter device having anengine and a first shaft rotatably mounted within a tube and rotatableby said engine, said attachment comprising: a propeller connected to asecond shaft; a protective shroud for said propeller and rotatablysupporting said second shaft; and connection means to interconnect saidshafts to permit their simultaneous rotation by said engine.
 2. A marinepropulsion device including a mounting swivel adapted to be mounted on amarine or riverine craft receiving said tube and permitting longitudinalmovement of said tube relative to said swivel, rotation of said tube inan azimuth plane, relative to said swivel, and rotation of said tube inaltitude relative to said swivel
 3. A marine propulsion device accordingto claim 1 or 2 wherein the connection means includes a drive reductiongearbox.
 4. A marine or riverine craft propulsion device, said devicecomprising a brush cutter having an engine, a shaft rotatably mountedwithin a tube and rotatable by said engine, a propeller rotatablymounted within a protective shroud for said propeller and rotatably byshaft, a mounting swivel adapted to be mounted on said craft receivingsaid tube and permitting longitudinal movement of said tube relative tosaid swivel, rotation of said tube in an azimuth plane, relative to saidswivel, and rotation of said tube in altitude relative to said swivel.5. A surfboard, surf-ski or like marine craft having an upper personsupporting surface and an under surface, a brush cutter device having anengine, a shaft rotatably mounted within a tube and rotatable by saidengine, a propeller rotatably mounted within a protective shroud forsaid propeller and rotatable by said shaft, said tube and shaft beinglongitudinally aligned with the longitudinal axis of said craft andpassing there through between said surfaces, said engine being locatedabove said upper surface and said propeller being located below saidlower surface, whereby said propeller is rotatable by said engine toadvance said craft through water, and said craft is steerable byaltering the weight distribution of said person.
 6. The surfboard,surf-ski or like marine craft according to claim 5, wherein said engineof brush cutting device is housed within a waterproof protective shroudfitted with a snorkel breathing attachment.